In many vehicles, an in-vehicle device is mounted to conduct information transmission through a wireless communication with respect to another device to execute various controls.
As one of typical examples, a smart entry system is provided. This system includes an in-vehicle device that is mounted in the vehicle, and a portable device (mobile device) that is carried by a user of the vehicle. The smart entry system is so structured as to execute the control of the locking/unlocking operation of vehicle doors or an engine start without manual operation of a mechanical key, when an authentication is satisfied between the in-vehicle device and the portable device through the radio communication.
As another example, a tire pressure monitoring system (TPMS) includes an in-vehicle device that is mounted in the vehicle, and tire sensors that respectively detect the air pressure or temperature of tires of the vehicle.
The TPMS is structured, for example, in such a manner that the tire sensors located at the respective wheels of the vehicle detect the air pressures of the tires and transmit the detected data by electric waves, and the in-vehicle device receives the electric waves from the tire sensors to monitor the air pressures of the tires.
Further, in the system of that type which conducts the radio communication, it is proposed to integrate two different kinds of systems together into a combined system (for example, U.S. Pat. No. 7,026,953 corresponding to JP 3789335). This combined system functions as a remote keyless entry (RKE) system when an ignition is OFF (engine is not in operation), and functions as the TPMS when the ignition is ON (engine is in operation).
In the above combined system, the RKE system and the TPMS can share the same parts of the configuration of the in-vehicle device. This makes it easy to spatially mount the system in the vehicle, resulting in reduction of costs.
The combined system including the RKE system and the TPMS does not cause any disadvantage, even if the RKE system does not operate when the ignition is ON.
However, if the combined system is constructed to include the smart entry system and the TPMS, the combined system does not function as a smart entry system when the ignition is ON unlike the RKE system.
More specifically, in the case of the smart entry system, the radio communication is required to continue intermittently or on the basis of given triggers regardless of ON/OFF of the ignition, thereby monitoring whether the portable device exists within the vehicle, or is taken out to the exterior of the vehicle.
For this reason, as disclosed in U.S. Pat. No. 7,026,953, when the in-vehicle device focuses on controlling the function of the TPMS merely because the ignition turns on, the in-vehicle device is incapable of appropriately implementing the radio communication with the portable device, thereby making it impossible to confirm the presence of the portable device.
Accordingly, the combine system disclosed in U.S. Pat. No. 7,026,953 needs be improved.